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Lab 3

Lab 3b – Reading a Push Button

GPIO Input Worksheet

1. What three DriverLib functions can setup a GPIO pin for input?

Hint, one place to look would be the MSP430 DriverLib Users Guide found in the

MSP430ware folder: \MSP430ware_1_60_01_11\driverlib\doc\MSP430F5xx_6xx\

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2. What can happen to an input pin that isn’t tied high or low?

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3. Assuming you need a pull-up resistor for a GPIO input, write the line of code required

to setup

pin P2.1 for input:

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4. Complete the following code to read pin P2.1:

volatile unsigned short usiButton1 = 0;

while(1) {

// Read push-button pin (SW1)

usiButton1 = ______________________________________________________;

if ( usiButton1 == GPIO_INPUT_PIN_LOW ) {

// If button is down, turn on LED

GPIO_setOutputHighOnPin( GPIO_PORT_P1, GPIO_PIN0 );

}

else {

// Otherwise, if button is up, turn off LED

GPIO_setOutputLowOnPin( GPIO_PORT_P1, GPIO_PIN0 );

} }

5. In embedded systems, what is the name given to the way in which we are reading the

button?

(Hint – it’s not an interrupt.)

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Check your answers against ours … see the Chapter 3 Appendix.

MSP430 Workshop - Using GPIO with MSP430ware 3 - 29

Texas Instruments MSP430 Student Guide

Other manuals for Texas Instruments MSP430